The broad aim of this research is to study the mechanisms by which tissue injury leads to induction of biosynthesis of C-reactive protein (CRP), Serum Amyloid A protein (SAA) and other acute phase proteins (APP). The serum concentrations of these proteins are markedly elevated in a variety of autoimmune diseases. In addition, these studies are relevant to the pathogenesis of amyloidosis. CRP bears close homology to serum amyloid P (SAP) protein, a constituent of all types of amyloid substances, which is itself an acute phase protein in the mouse, although not in man. SAA is closely related to protein AA, the major fibrillar protein in secondary amyloid tissue, and may be its precursor. These studies will seek to demonstrate and characterize the mediator substances ultimately responsible for induction of APP synthesis by hepatocytes, to define the cell or cells of origin of these inducer substances, and to delineate the mechanisms by which tissue injury causes these cells to produce APP-inducers. We will begin studies designed to elucidate the molecular mechanisms governing expression of the CRP gene. We will employ in vitro cell culture techniques to demostrate induction of CRP, SAA and serum glycoprotein synthesis by rabbit primary hepatocyte cultures. Particular emphasis will be placed on detection of APP inducers in secretory products of activated phagocytic cells. We will utilize physicochemical techniques to characterize the CRP-inducers already detected in acute phase serum in preliminary studies. The difference between CRP and SAA inducers will be investigated and their cells of origin identified. Should these prove to be phagocytic cells, products of tissue breakdown will be studied for their ability to cause release of APP-inducers from these cells. We plan to measure the rate of synthesis of CRP-specific mRNA during in vivo induction, using refinements of the methodology employed for eukaryotic mRNA isolation and translation in heterologous, cell-free protein synthetic systems.